Improved Tumor Targeting and Longer Retention Time of NIR Fluorescent Probes Using Bioorthogonal Chemistry

Abstract

The traditional labeling method for targeted NIR fluorescence probes requires directly covalent-bonded conjugation of targeting domains and fluorophores in vitro. Although this strategy works well, it is not sufficient for detecting or treating cancers in vivo, due to steric hindrance effects that relatively large fluorophore molecules exert on the configurations and physiological functions of specific targeting domains. The copper-free, “click-chemistry”-assisted assembly of small molecules in living systems may enhance tumor accumulation of fluorescence probes by improving the binding affinities of the targeting factors. Here, we employed a vascular homing peptide, GEBP11, as a targeting factor for gastric tumors, and we demonstrate its effectiveness for in vivo imaging via click-chemistry-mediated conjugation with fluorescence molecules in tumor xenograft mouse models. This strategy showed higher binding affinities than those of the traditional conjugation method, and our results showed that the tumor accumulation of click-chemistry-mediated probes are 11-fold higher than that of directly labeled probes. The tracking life was prolonged by 12-fold, and uptake of the probes into the kidney was reduced by 6.5-fold. For lesion tumors of different sizes, click-chemistry-mediated probes can achieve sufficient signal-to-background ratios (3.5-5) for in vivo detection, and with diagnostic sensitivity approximately 3.5 times that of traditional labeling probes. The click-chemistry-assisted detection strategy utilizes the advantages of “small molecule” probes while not perturbing their physiological functions; this enables tumor detection with high sensitivity and specific selectivity.

Cell Tracking in Cancer Immunotherapy

“…The CC49 antibody recognizing the tag72 antigen derivatized with trans-cyclooctene (TCO) was used for pretargeting 111 In-labeled DOTA-dipyridyltetrazine, demonstrating fast and high tumor activity uptake and high tumor to muscle ratio in a mouse model. Using small binding proteins such as diabodies or affibodies instead of intact IgG antibodies improves the pretargeting performances for PET (62,63). Pretargeting may also be applied to NIR fluorescence imaging (63).…”

“…Using small binding proteins such as diabodies or affibodies instead of intact IgG antibodies improves the pretargeting performances for PET (62,63). Pretargeting may also be applied to NIR fluorescence imaging (63).…”

A Light‐Up Probe with Aggregation‐Induced Emission for Real‐Time Bio‐orthogonal Tumor Labeling and Image‐Guided Photodynamic Therapy

“…This can collectively realize tumor‐specific imaging and tumor‐targeted drug delivery, which is more effective than traditional active targeting strategy owing to the covalent ligation . Furthermore, in contrast to the active targeting strategy that relies on existing receptors on cell surface, the artificial receptors can be expressed on cells in large quantity regardless of the phenotype of tumor cells, which can further enhance the uptake of imaging agents or drugs on tumor sites through bio‐orthogonal reaction.…”

Amplifying Nanoparticle Targeting Performance to Tumor via Diels–Alder Cycloaddition

“…With functionalization of biological ligands (such as peptide, aptamer, and antibody), these nanoparticles are expected to be endowed with capability to further actively target tumors . Efficient binding of nanoparticles to the receptors on the cell surface can increase their accumulation at the tumor sites, while those unbounded will be rapidly cleared . Unfortunately, the insufficient, unstable, and nonhomogeneous expression of these receptors in tumor tissues limits the targeting efficiency .…”